Harlequins returned to the top of the Aviva Premiership table with a 31-26 bonus point victory over London Welsh at the Kassam Stadium on Sunday.

Following a totally one-sided first half Harlequins led 21-6. It should have been far more and a huge defeat for the Welsh seemed likely. However, in a complete turnaround, Welsh played with great spirit in the second half to reduce the arrears to 24-19 and a remarkable comeback was on the cards before the visitors steadied the ship to run out narrow winners.

Harlequins rested England internationals Mike Brown and Ugo Monye from their matchday squad while the injured Gavin Henson was not ready to return for London Welsh.

Quins signalled their attacking intentions from the start as Ollie Lindsay-Hague fielded the kick-off deep inside his own 22 before setting off a sweeping movement which took the visitors into the home 22. George Lowe and Nick Evans both made vital contributions to the movement but an over-ambitious pass from Danny Care prevented Quins from opening the scoring.

The visitors continued to dominate but missed another chance when Evans was wide with a straightforward penalty attempt but with 15 minutes gone they took the lead with an individual try from Care. The scrum-half brushed aside some very weak Welsh tackling to run 15 metres for the score, which Evans converted.

The visitors threatened the Welsh defence almost at will and they soon extended their lead with a second try. Sam Smith did the spadework with a weaving run to create the score for Lowe, which Evans again converted.

Welsh were dealt another blow when lock Kirill Kulemin was shown a yellow card for a high tackle on Evans but they got on the scoreboard when Gordon Ross kicked a penalty after Quins were penalised at a scrum.

Kulemin returned but only in time to see his side concede a third try when Chris Robshaw barged over from close range. Evans converted but a second penalty from Ross made it 21-6 to the visitors at half-time.

Another careless pass from Care placed his side under pressure with Welsh wing Nick Scott being hauled down narrowly short. The hosts then had their best period of the match and should have scored but number eight Adam Balding chose to drive for the line instead of passing and was held up by the combined efforts of Evans and Tom Guest.

Welsh declined two kickable penalties in favour of more attacking options but when awarded two more, Ross made no mistake with both kicks for a 21-12 scoreline going into the final quarter.

The Quins were shaken but their nerves were calmed when Evans was successful with a penalty as Welsh committed another offence at a scrum. Back came the hosts to collect their first try when Scott cleverly dummied over for the score, which Ross converted to reduce the gap to only five points.

With 13 minutes remaining Quins made the game safe with their bonus-point try, as Evans finished off some neat inter-passing with the outside-half converting for a match tally of 16 points.

Ed Jackson's interception try - converted by Ross - brought Welsh back within an unconverted try of Quins, but the visitors held on in a frenetic finish which also featured yellow cards for Quins lock George Robson and Welsh prop James Tideswell.

Despite seeing his side return to the Premiership summit, Quins boss Conor O'Shea was fuming at the final whistle following the performance of referee Llyr Apgeraint Roberts. "I'm unbelievably frustrated, you'd have to go a long way to see worse," he said of Mr Roberts' display.

"Everything was wrong - it was incredible. The offside line was irrelevant, trailing runners coming back was irrelevant, backing into the maul, not releasing in the tackle - all irrelevant. We were 21-6 at half-time but bafflingly the penalty count was against us, how can that be? We have a feedback process for the referees but it's not actioned upon and it's very difficult at times."

London Welsh head coach Lyn Jones praised his side's effort that earned them what could be a valuable bonus point. "At half-time we were staring down the barrel," he said, "We started the second half well, we were still in there and we needed to get the first score, which we did. We had a chance to win but their class and ability shone through in the end. They are a very good side and it's a pity more sides don't play like them.

"We are showing determination and spirit and are good enough to stay in this league."